This invention relates to the mixing region of the fuel nozzle assembly for a combustor in a gas turbine burning on Syngas or hydrogen fuels. Less forgiving properties of hydrogen (H2) and syngas fuels such as higher flame speeds, lower ignition times makes it impossible to use prior art designs applicable only for burning natural gas fuels.
Industrial gas turbines have a combustion section typically formed by an array of can-annular combustors. Each combustor includes a fuel nozzle mixing region that provides specified amounts of fuel-air mixture to a combustion zone within the combustor. The fuel-air mixture is allowed to burn inside the combustion zone to generate hot, pressurized combustion gases that drive a turbine.
Natural gas, e.g., primarily methane, is a common fuel for industrial gas turbines. Rapid depletion of hydrocarbon resources has led to an increased focus on using coal derived H2 and/or syngas for industrial gas turbines. The flame speed of hydrogen and syngas is significantly higher, e.g., six to seven times faster, than the flame speed of natural gas. The burner needs to be designed to operate for greater flame speed of hydrogen and syngas which could increase the propensity for flame flashing back in to the mixing region of the fuel nozzle assembly. Flame holding in the unburnt mixing region has the potential to damage the components of the nozzle assembly. There is a strong need to design and develop devices and methods to prevent propagation of flame into the fuel nozzle assembly.
Syngas refers to a gas mixture available in varying amounts of carbon monoxide and hydrogen generated by the gasification of a carbon containing fuel to a gaseous product. Syngas examples include steam reforming of natural gas or liquid hydrocarbons to produce hydrogen, the gasification of coal and in some types of waste-to-energy gasification facilities. Syngas is combustible and often used as a fuel source. Syngas may be produced, for example, by gasification of coal or municipal waste.
Existing combustor operating on natural gas may need major modifications to accommodate additional burning of hydrogen and syngas fuels. For example, the higher flame speed of hydrogen and syngas (as compared to natural gas) may require combustor adjustments to ensure that the flame is stabilized in the combustion zone and does not propagate upstream into the mixing region of the fuel nozzle assembly. There is a strong need to develop methods and devices to modify the existing natural gas combustor designs to allow burning of hydrogen and syngas fuels.